With the rapid development of mobile smartphone and its built-in location-aware devices, people are possible to establish trust relationships and further interaction with each other based their matched interests, hobbies, experiences, or spatiotemporal profiles. However, the possibility of...

Wireless sensor networks (WSNs) is a key technology which is deployed under the assumption that participating sensors are cooperative in forwarding each other's packets. However, some nodes may behave selfishly by dropping other's packets or refusing to provide services in an attempt to maximize...